1. Go to Settings by selecting the gear icon in the main navigation menu.
2. Select the “My Fire TV” option. (If you are using a Fire TV Smart TV, then select the “Device & Software” option.)
3. Select the “About” option.
4. Repeatedly select the first option, which should be the name of your device, such as “Fire TV Stick” or “Fire TV Stick 4K.” You will need to select it about 7 times. As you select it, you’ll see countdown text appear near the bottom of the screen indicating how many more times you need to select it.
5. Once you’ve selected the first option enough times, the text “No need, you are already a developer” will appear at the bottom to indicate that developer mode has been enabled.
6. You can now back out one menu level by pressing the BACK button on your remote and you will see the “Developer Options” menu item. From there you can turn on ADB debugging or enable installing unknown apps.